async void SendEmail(object sender, EventArgs e)
        {
            ServiceManager manager = new ServiceManager();
            var            model   = new IEEEContactModel
            {
                email   = txtEmail.Text,
                name    = txtNameSurname.Text,
                message = txtMessage.Text
            };

            var result = await manager.SendMessage(model);

            DisplayAlert("Sonuç", result, "Ok");
        }
        public async Task<string> SendMessage(IEEEContactModel model)
        {
            using (HttpClient client = new HttpClient())
            {
                client.DefaultRequestHeaders.Add("Accept", "application/json");

                var request = await client.PostAsync(baseUrl,
                    new StringContent(JsonConvert.SerializeObject(model),
                    Encoding.UTF8, "application/json"));

                if (request.StatusCode == HttpStatusCode.OK)
                {
                    var response = await request.Content.ReadAsStringAsync();
                    return response;
                }
                else
                {
                    return "Bir hata oluştu. Lütfen daha sonra tekrar deneyiniz.";
                }
            }
        }